# -*- coding:utf-8 -*-
class Solution:
    def __init__(self):
        # 先要初始化两个stack
        self.stack_1 = []
        self.stack_2 = []
    def push(self, node):
        self.stack_1.append(node)
        # write code here
    def pop(self):
        while(self.stack_1):
            self.stack_2.append(self.stack_1.pop())
        
        num = self.stack_2.pop()
        
        while(self.stack_2):
            self.stack_1.append(self.stack_2.pop())
        
        return num